1. Field of the Invention
The present invention relates to an air temperature control system for use in vehicles such as private cars, trucks and buses.
2. Description of the Prior Art.
As shown in FIG. 1, an air temperature control system for use in motor vehicles in the prior art, which is generally designated by reference numeral 1, comprises a fan 2, an evaporator 3, a room heater 4 and the like. The evaporator 3 is cooled by operation of an expansion valve 5, a condensor 6 and a compressor 7. The compressor 7 is connected via an electromagnetic clutch 8 to an engine 9 for driving a vehicle. Cooled air leaving evaporator 3 is directed toward room heater 4 which is provided with heat by coolant water leaving the engine 9. Room heater 4 is provided with an air-max damper 10, the angle of which may be adjusted to divert a desired portion of the cooled air through the heater prior to being directed into the passenger compartment (room) of the vehicle, in order to regulate the room air temperature.
In such an apparatus, due to the fact that the air temperature at the outlet of the evaporator 3 is controlled to be held constant, energy loss through reheating a portion of the cooled air is potentially very large. In an improved system which takes energy saving into consideration, the relation between the temperature of the air at the outlet of evaporator 3 and the position of the air-mix damper 10 is controlled as illustrated in the diagram provided in FIG. 2. Such control is provided by a potentiometer 12 for detecting the position of the air-mix damper 10 as normally coupled to an actuator 11 and a thermistor 13 for detecting the temperature of the air at the outlet of evaporator 3. Moreover, compressor 7 is controlled via electromagnetic clutch 8 to be turned ON and OFF so that the air temperature at the outlet of evaporator varies linearly in proportion to the variation of the position of the air-mix damper 10. However, even such an improved system has a shortcoming that it is not as energy efficient as it might be and its temperature regulation is insufficient. The present invention improves upon the temperature regulation and energy efficiency of the prior art systems.